Signal processing circuits are frequently used to read storage media and interpret obtained analog signals as discrete values stored on the media. For magnetic storage media, a transducer head may fly on a cushion of air over a magnetic disk surface. The transducer converts magnetic field variations into an analog electrical signal. The analog signal is amplified, converted to a digital signal and interpreted (e.g., using maximum likelihood techniques, such as using a Viterbi detector). Tracking of stored data during a read operation is frequently performed using feedback or decision aided gain and timing control. Additionally, perpendicular magnetic recording techniques can be used to increase the amount of data stored on a magnetic medium.
As the amount of data stored on a magnetic medium is increased, a higher error-rate can result unless error detection and correction techniques are used to compensate. Post-processing is often used to improve the error-rate performance of the main detector in magnetic recording systems. For example, a post processor, such as a media noise processor (MNP), can process detector output in a read channel to improve performance. Additionally, direct current (DC) correction circuitry is sometimes used to reduce DC distortion before the main detector.